Sunday, May 15, 2016

Longer Fasts, Ketoacidosis and Weight Regain

Ask Dr. Jason Fung

There are tons of questions about intermittent fasting, like these

  • Should you expect to regain some of the weight lost after breaking a long fast?
  • Ketones tend to go up during longer fasts – is there a risk of ketoacidosis?

Dr. Jason Fung is one of the world’s leading experts on fasting for weight loss or diabetes reversal. Here are a his answers to those questions and more:

Fasting, ketoacidosis and weight regain

I’m not diabetic and I’m not on any medications. I’m now 5.5 days into my 7-day fast and I feel great! I’ve been monitoring my blood sugar and ketone levels every 12 hours. Over the 5.5 days my blood sugar average is 81 and my ketone average is 4.1. This morning my blood sugar was 66 and ketones 5.4. I don’t think I should be concerned about ketoacidosis but I can’t help it, as my ketones get progressively higher I can’t stop thinking about it. Please put my concerns to rest…

Is there any risk of my ketones going too high if I’m NOT a type 1 diabetic? I have been at a weight loss plateau for months even while eating strict LCHF and following a 16:8 eating plan. In the 5.5 days of fasting I’m down 7 lbs! In your weight loss management program, do you find clients are able to keep the weight off (after a long fast) when going back to an LCHF eating plan?
Thank you so much!!!!

Ketoacidosis mostly happens in type 1. Ketones are supposed to go up during fasting – it’s called starvation ketosis.

There will usually be some weight regain after the fast, so be prepared. Generally, you can expect to lose 1/2 pound per day of fasting on average. For 7 days, that’s 3 1/2 pounds. Everything else could be water weight which will come back, and it would still be OK. It doesn’t mean the fast didn’t work.
Dr. Jason Fung

Very low blood sugar

Hello Dr. Fung,
I just started fasting after reading your blog post series. I’ve never tested blood glucose before and thought I’d try it with this fast and just bought a meter. I know you can’t give specific medical advice, but could you tell me from your experience with your patients…Do you feel a blood glucose reading of 39 on Day 3 of a fast falls within acceptable levels or do you feel that is too low? I have no symptoms and feel fine.



If you are taking diabetes medications then yes, it is too low. If not, the main thing is to make sure you are feeling well.

Dr. Jason Fung

Higher blood glucose when fasting

Hi Dr. Fung,
I was diagnosed with type 2 a month ago. my fasting glucose was 386. I started fasting and LCHF and now a little less then a month later my average number is 115! My Dr. wanted to put me on medication and I said no I will try this 🙂 So glad I found your Youtube video! I am wondering why sometimes when I fast for 34-48 hours my glucose is actually higher then on days I am eating?


Dr. Jason Fung: This is similar to the Dawn Phenomenon, Read my post here –

Dr. Jason Fung


More Questions and Answers

Many more questions and answers:

Intermittent Fasting Q&A

Read all earlier questions and answers – and ask your own! – here if you are a member:

Ask Jason Fung about intermittent fasting and type 2 diabetes – for members (free trial available)

Read Dr. Jason Fung’s new great book The Obesity Code for many more insights:

The Obesity Code

Videos About Intermittent Fasting and Diabetes

What is Fasting? – Dr. Jason Fung4.4 out of 5 stars5 star67%4 star16%3 star8%2 star2%1 star4%403 ratings40305:21How to Maximize Fat Burning – Dr. Jason Fung4.7 out of 5 stars5 star83%4 star7%3 star5%2 star0%1 star2%216 ratings21603:52How to Fast – The Different Options – Dr. Jason Fung4.9 out of 5 stars5 star90%4 star6%3 star0%2 star1%1 star0%102 ratings10206:47

The 7 Benefits of Fasting – Dr. Jason Fung4.7 out of 5 stars5 star84%4 star6%3 star3%2 star2%1 star4%99 ratings9907:33The Top 5 Myths of Fasting – Dr. Jason Fung4.9 out of 5 stars5 star92%4 star5%3 star1%2 star1%1 star0%89 ratings8908:23Breakfast! Is It Really That Important? – Dr. Jason Fung4.7 out of 5 stars5 star86%4 star4%3 star3%2 star3%1 star1%81 ratings8107:08

The Most Common Questions – Dr. Jason Fung4.7 out of 5 stars5 star84%4 star6%3 star6%2 star3%1 star0%33 ratings3305:385 Tips to Make Fasting Easier – Dr. Jason Fung4.8 out of 5 stars5 star83%4 star10%3 star4%2 star2%1 star0%49 ratings4905:19How to Get Started with Fasting – Dr. Jason Fung4.5 out of 5 stars5 star71%4 star12%3 star9%2 star4%1 star1%113 ratings11302:30

The Power of a 7-Day Fast – Dr. Jason Fung4.6 out of 5 stars5 star74%4 star18%3 star6%2 star2%1 star0%50 ratings5003:34Who Is Dr. Jason Fung?4.4 out of 5 stars5 star68%4 star14%3 star12%2 star4%1 star1%98 ratings9801:56The Perfect Treatment for Weight Loss and Diabetes – Dr. Jason Fung4.6 out of 5 stars5 star78%4 star9%3 star6%2 star4%1 star1%92 ratings9245:20

The 2 big lies of type 2 diabetes – Dr. Jason Fung4.6 out of 5 stars5 star82%4 star6%3 star4%2 star6%1 star0%62 ratings6242:54The Key to Obesity – Dr. Jason Fung4.5 out of 5 stars5 star76%4 star8%3 star8%2 star1%1 star3%78 ratings7844:22How to Reverse Diabetes Type 2 – Dr. Jason Fung4.9 out of 5 stars5 star90%4 star9%3 star0%2 star0%1 star0%21 ratings2110:23

The Etiology of Obesity – Dr. Jason Fung4.7 out of 5 stars5 star92%4 star0%3 star0%2 star4%1 star4%25 ratings2538:45

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